Bio-defense, communicable disease control, and surveillance of emerging infections are essential functionsof public health. Infectious disease threats to public health encompass deliberate attacks, novel organisms,novel variants of old pathogens, antimicrobial-resistant strains, and new susceptible human populations.However, even familiar microorganisms are still major causes of morbidity and mortality. Strategies to betterguide public health policy- and decision-making, particularly in situations of high uncertainty and high risk,are urgently needed.To address this problem, this project brings together four disciplines: public health, mathematical modeling ofinfectious diseases, computer simulation of complex systems, and cognitive psychology. The overall goal iscreate an integrated data and simulation environment for public health decision support adapted to thefactors that drive public health decision-making. Three lines of research will proceed in parallel during thefirst half of the project. One line comprises the investigation of decision-making processes of public healthepidemiologists and policy-makers using methods drawn from the discipline of cognitive psychology. Anotherline of research will entail the development of a detailed simulation of an urban population modeled after theSalt Lake Valley. A unique contribution of this specific part of the study is the evaluation of the impact ofincorporating novel sources of data regarding demographics, activity levels, and health status into theestablishment of the synthetic population. A third line of research will be to evaluate the conceptualizationand interpretation of mathematical models of infectious disease by public health epidemiologists and policymakers.These research lines will then come together in four significant ways. First, the computersimulations will provide a more precise instrument to probe the factors that influence decision-making.Second, the information obtained from the analysis of decision-making processes will in turn inform thedesign of the prototype simulation test bed. Third, the simulations will facilitate investigation of transmissionmodel acceptability for public health personnel. Fourth, a prototype simulation test bed will be deployedinteractively in which the public health epidemiologist and policy-maker will be able to visualize multiplecourse of action and their effects, when confronted with a simulated outbreak.